UNWERSJi^ V LiBEARIES Iat 514 'Markham, J. H. iThe preparation of salicylic 1 acid from phenol Digitized by tine Internet Arcliive in 2009 witli funding from CARLI: Consortium of Academic and Researcli Libraries in Illinois http://www.archive.org/details/preparationofsalOOmark The Preparation of Salicylic Acid FROM Phenol a thesis PRESENTED BY J. H. MARKHAM AND B. W. LEWIS TO THE PRESIDENT AND FACULTY OF ARMOUR INSTITUTE OF TECHNOLOGY FOR THE DEGREE OF BACHELOR OF SCIENCE IN CHEMICAL ENGINEERING MAY 29, 1919 APPROVED I'lnA-^scr of C ^(.r i.f CtKiiiicnl KiiK'iitrcrinsr ^H\C^GO. ^^ " Dran of Cultunil Sl.iilies I H D S X PAGE PROBLEM 2 OCGUEHENCE MD LETHODS OF PREPAHATIOil 3 KOLBE'S PROCESS 7 PHYSICAL PROPERTIES 10 CHEMICAL PROPERTIES 14 USES 0? SALICYLIC ACID 20 OUR I.IETHOD OP PREPARATIOII 25 EXPSRIMEITTAL RUIIS 30 PURIEICATIOE 3^ THE CHEMISTRY OE TEE SCHMIDT METHOD 36 COECLUSIOH ^° REEEREKCES ^^ 2S1S5 1. This work v;as done under the general direction and supervision of Professor Harry McCormack, for which respectful acknowledgment is hereby made. PROBIEI.I. Preparation of Salicylic acid from phenol. Using phenol as a starting substance to prepare the acid, to study the process and to purify the product. It was originally in- tended to start v.ith tenzol and go thru the synthesis of sodium phenate, tut since the price of phenol has reached such a lov; price, and since the synthesis of phenol is now more or less standard, the process starts with phenol and caustic soda. OCCUnRElJCE AllD LIETHODE OF PP.EPAHATIOIT . Ortho-hyuroxy-carboxylic acid, or ortho-hydroxy-'bensoic acid or ortho-hydroxy- c art oxy-b eri z ene . C H 7 6 3 C H . OH.COOH (1-2) 6 4 COOH H OE H H E The acid v.as first discovered by H. Piria in 16S9, by fusing salicylic alde- hyde v;ith potassium hydroxide. Calhours proved in 1843 that oil of v.intergreen is mainly methyl salicylate. In 1653 A. Ho f nan converted anthranilic acid into salicylic acid by means of nitrous acid. Finally Ilolbe and lautemann prepared it synthetically from phenol, sodium and carbon dioxide in 1673. Natural salicylic acid is found in many plants, usually in the form of methyl salicylate or oil of v.inter^reen C^H fOH)COOOII- 6 4 3 The acid may be obtained from the following plants: Gaulterla fragrantissima, Gaulteria procumbeus, Gaulteria punctata, Gaulterla leukocarpa, Betula lenta, Llonotropa hypopitis, Spiraea ulmaria, Gloria superba and from many other plants. The acid is also found in very small quantities in some grapes, strav,- berries, cherries and in fact in most fruits. Salicylic acid may be prepared by one of the following methods: 1. 3y oxidation of, or by fusion vfith potassium hydroxide, or by electrolysis of one of the following substances; salicin, salicyc aldehyde, and saligenin. 2. 2y fusing potassium hydroxide with one of the following substances; benzoic acid. indigo, coumarin, ortho-chlor-benzoic acid, ortho- toluene Bulphonio acid , ortho-cresol-sulphonic acid, ethyl-cresol-sulphonic acid. 3. By heating with water ortho-diazo- amldobenzoic acid. 4. By dry distillation of calciutn salt of anie acid or meta-oxybenzoic acid. 5. 3y reaction of potassium permanganate on the potassium salt of o-cresolsulphonic acid. .6. By heating phenol with carbon tet- rachloride and alco::olic potash; p-oxybenzoic acid is here also obtained. C H OH+CCl + 6 KOE -* C H .OZ.GOOX * ZOL *■ 6 5 4 6 4 SHgO 7. By oxidation of toluene ortho-phos- phonic acid with alkaline potassium permanganate. 8. By distillation of sodium phenyl car- bonate in a current of carton dioxide with sodium phenate. 9. By action of nitrous acid on anthranilic acid. 10. By electrolysis of a solution of ben- zoic acid ii) acetic acid. 11. By exposing a solution of benzoic acid to the sunlight in the presence of a ferric salt. 1£, By passing dry carbon dioxide into a hot mixture of phenol and sodium. (Kolbe and lautemann) KOIBE'S PROCESS. This method has teen used for the manu- facture of salicylic acid on a large scale. Equivalent quantities of pure phenol and a concentrated solution of sodium hydroxide are thoroughly mixed and evaporated to dryness in iron vessels with constant stirring. When the mass is dry it is pulverized, placed in a metal retort and heated to 100°C while a current of heated dry carton dioxide is passed in. The mass is kept well stirred and the temperature is slow- ly raised to 180°G. This operation takes several hours. After the retort has ceen heated for some time the phenol begins to distill over. V/hen the evolution of phenol ceases, the temperature is raised to 200°C and the operation stopped. When the mass has cooled, it is dissolved in v.ater and the resinous substances precipitated with a miner- al acid, a further addition of acid precipitates salicylic acid, which is then purified. This process may be regarded as taking place In four stages: 1. Phenol and sodium hydroxide form sodium phenate:- C-HpOH ^ ITaOH ^ C-H^ONa *■ H^O 6 5 6 5 E E. Carton dioxide when added to the sodium phenate forms sodium phenyl cartonate:- C^H^OHa * CO^ = C^H^.OCO^.lTa 6 5 E 6 5 E This stage is completed v.hen the mass is heat- ed to about 110°G for one hour. 3. The sodium phenylcartonate is trans- formed into sodium salicylate:- C^H^.OCO^.lIa = C^H,.0H.C001Ia 6 5 £ 6 4 The COg goes into the Ortho-position tetv.-een the hydrogen atom and the neucleus, producing a caroxyl group. 4. In the last stage the salt acts with some unchanged sodium phenate and sets free the TDhenol in the disodium salt C H .OH.COOIIa-C H^.OlIa = C H .Ol^Ta.COOlIa * G H^OH 64 65 64 65 This change takes place during the last stage of heating. 10, physicjVI properties . Salicylic acid crystallizes irotn ^vater in long white needles, having a sweetish astrin- gent taste. From alcohol salicylic acid crystal- lizes in large colorless monoclinic prisms. The acid, has a specific gravity of 1.48£ - 1.465 at 4^0; melting point 158° - 159°3. Pure salicylic acid dried in vacuum over sulphuric acid gives a melting point of 158, 5°C. Small amounts of p-hydroxybenzoic acid lower the melt- ing point. ".Vhen slov/ly heated to 200°G is sub- limes, and on cooling deposits in long fine needles; when rapidly heated to 200°C it vala- tilizes and the vapors undergo a partial dis- sociation into phenol and carton dioxide, accord- ing to the formula: ? a^ k : 254.9 l-a2 7/here P^pressure in cm. of mercury, a=rdegree of dissociation. This is an irreversible reaction. 11. Heat of comTDustion of salicylic acid is 5162 cal. per gram or 754990 cal. per mole- cule. Heat of formation from phenol 5520 cal.; latent heat of futic/. - 6550 cal.; heat of neu- tralisation of a solution of the acid with l/E molecule of sodium hydroxide 12910, and v.-ith another half molecule .810 cal. Salicylic acid is slightly soluble in cold vvater or petroleuoi ether, hut (luite soluble in hot water. 0° 1.24 35° 5.51 70^ 15.70 5° 1.29 40° 4.16 75° 17.55 10° 1.55 45° 4.69 80° 22.08 15° 1.64 50° 6.56 85° 27.92 20° 2.00 55° 7.44 90° 57.55 25° 2.46 60^' 9.00 95° 50.46 30° 2.98 65° 10.94 100° 75.07 12. The acid is very soluble in chloroform, alcohol, ether, aceton and ethyl acetate. 100 parts of ether dissolve at 15° 50.47 of acid 100 100 100 100 100 100 absolute alcohol dissolve 49.65 of acid 90;'o 42.09 SI. 20 .97 .50 .10 " aceton " " benzene " " glycerin " " petroleum ether " The solubility of salicylic acid is con- siderably increased in the presence of so;:ie salts: One part of salicylic acid in v;ater in the presence of 1 part of potassium nitrate dissolves in 50 parts 1.5 " " ammonium citrate " " 60 " E " " sodium sulphite " " 50 " E " " sodium phosphate " " 50 " 2^5 »» " i» w " "12.5 " 15. Chloroform or ether remove it from Vv'ater solutions. Salicylic acid can "be distilled in steam. The para-acid and traces of the meta- acid usually accompany the ortno-acid if extreme care is not ohserved in preparation. S.G. H. ?. Sol. in water Chloro- form PeOlg o-acid OH GOOH] 1.4855' 1580G' 1:1000(150) ' Very ' Violet (;-i) m-acid OH COOH 1.475 200° 1:106 insol. Ho chani 0-3) p-acid OH GOOH 0-4) 1.465 • £15° 1:126 t Slight ' ly T ' Yellov; i flacc. ' ppt. The ortho-acid is the only one of im- portance. 14. CHEMICAL PROPiiRTIES. Salicylic acid is both an acid and a phenol. It forms three sets of salts; acid, "basic and neutral, as well as ethers. '.Vhen heated to 200° G it decomposes into phenol and carbon dioxide CgK^.OH.COOH ■= GgHg.OH * CO^ Heated in a closed vessel with water it decomposes into phenol and carbon dioxide at 2E0°-230°; a similar decomposition takes place when treated with con. hydrochloric or hydrobromic acid, or with dil. sulphuric at 140°-1500 , or with con. phosphoric at 120°. Phosphorus trichloride gives qjI^ClPOg, which is decomposed by water into salicylic acid and phosphoric acid. When treated with phosphorous pentachloride and the products distilled, ortho- chlorbenzoylchloride is obtained. Phosphorous pentabromide yields raonobrom-salicylic acid, and this on heating with alcohol or phenol gives the 15, esters of salicj^lic acid. Phosphorous oxychloride gives on heating salicylic anhydride. Salicylic acid or its salts give a deep violet coloration in a neutral solution v/ith fer- ric salts. This reaction is used for qualitative as well as quantitative determinations of sali- cylic acid. 2his test is sensitive to about 1:550,000. Hov/ever phenol or salicylic aldehyde give the same test. The color is not removed hy acetic acid. This test fails, if for one part of salicylic acid there is present 365 parts of sodium nitrate or 36 parts of sodium chloride. Dry hot ammonia breaks up salicylic acid into phenol and carbon dioxide. On oxidation with potassium bichromate in sulphuric acid carbon dioxide and v.ater are produced. Potassium chlorate and hydrochloric acid oxidize it to chloranil. Potassium permanganate oxidizes it to formic acid and carbon dioxide. 16, On oxidation witli potassium persul- phate in an alkaline solution and subsequent colling with an acid hydroquinone carboxylic acid is obtained. Chlorine forms mono- and di- substitu- tion products. Dil. nitric acid forms nitro-salicylic acid, while con, nitric acid forms picric acid. Sodium amalgam in the presence of boric acid produces salicylic aldehyde. On heating v/ith resorcin it gives tri- oxybenzophenone. Sodium and amyl alcohol reduce it chiefly to pimelic acid. Concentrated sulphuric acid gives mono- sulpho-salicylic acid. By heating v.ith concentrated sulphuric acid and potassium ferrocaynide phthallc acid is obtained. xhe same product is obtained when salicylic acid is heated vvith oxalic acid and glycerin. 17, Y/hen salicylic acid is heated with "butyl alcohol and zinc chloride a homologue 01 the acid is obtained, which on distillation goes into tutyl phenol. It cotahines v^ith diazo-hodies to form azo-compounds. nitrous acid passed into an etherial solution of salicylic acid gives nitro- and diaao-oxyhenzoic acids. At 210° aiiiline gives phenol and C.H^(OH).GOIIPhH. o 4 Gyanamide and alcohol at 100° form urea and ortho-oxybenzoic ether. Phenol and stannic chloride at 120° give op-di-oxy'benzophenone, V.'ith camphor it forms a compound C H 0„2G, H 0, which melts at 50°. 7 6 3 10^5 • On heating with soda lime phenol and carton dioxide are formed C^H, (OH) GO. OH ♦ Geo = C,H_OH - GaCO_ 6 4 o 5 o 16. Potassium persulphate added to a solution of salicylic acid and potassium hy- droxide forms a crystalline compound C H (CO K)OSO K A solution of salicylic acid and borax in water deposit crystals of a composition 4 10 7 Chloral forms with it at 140^^ ^ 4 cue 5 In dilute aqueous solutions "bromine water gives a x>recipitate of C;.Hr;Br.O, « -^ -^ Oct Iodine and potash give a red pov.der GgH^KODCOgZ. It forms compounds with casein, fihrim and albuminoid, containing about 14;j of the acid and having a foraiula — *^7E^11 ^^'18^^82 2C H . It melts at 40°, and is soluble in 7 6 S water to an extent of ,0051 parts in 100 parts of water. 19. ■".'.Tien taken Internally it is excreted as salicyluric acid or salicyl-glycocoll — EO, USES 0? SAIICYLIC ACID. Salicylic acid is largely used in the preparation of pharmaceuticals. The acid is also of importance in the manufacture of syn- thetic chemicals, such as dye stuffs. Its chief pharmaceutical uses are as an antirheumatic and as an antiseptic. Llany states and countries forhid its use as a food .preservative in which field it formally found one of its largest uses. The acid finds extensive use in the production of salicylates. V/hen ethyl alcohol and sulfuric or hydrochloric acid reacts with the salicylic acid, ethyl salicylate results. Llethyl salicylate, oil of wintergreen may be pre- pared from methyl alcohol and the acids in the same manner. Llethyl salicylate is extensively prescribed for external uses. Allyl salicylate which is prepared in the manner as described above, is used both medicinally and as a perfume. Phenyl salicylate, Salol , another derivative of the acid is a very important pharmaceutical; but because of its cost, other salicylates are sub- 21. stituted. V/hen phosphorous oxychloride is allowed to react with the acid phenyl sali- cylate is thus formed. Acetyl salicylic acid, "Aspirin", is prepared from salicylic acid and acetyl chloride. "Aspirin finds extensive use in the treatment of rheumatic conditions. All of the Salicylic preparations taken internally, are used for T;he henefit of the salicylic acid v/hich is liberated in the decomposition of the compound. Quinine salicylate is one of the few compounds, prepared directly from the sodium salt. Among the most important salicylic salts vi'hich are used in the preparation of anti- rheumatic compounds are: tolypyrinesalicylate , salicylic-sulfonic acid, salicylamide, salicyl-a- methyl -phenyl -hydrazone and methl-acetyl-salicylate. It is interesting to note that in the production of the raethyl-acetyl-salicylate, anhydous zinc chloride is said to act as a catalytic agent. B2. The next important use of salicyio acid is in the synthesis of many important organic ■bodies. The first of these "bodies to receive consideration is Saligenin. CH OH £ (y-3) OH This "body is prepared from salicylic acid, thru the amide, and the reduction of the latter with sodium amalgam in acid solutiOii. Trichlor-a-a-glyceric acid is pre- pared by the action of potassium chlorate and hydrochloric acid upon salicylic acid. V/hen salicylic acid is iodised by various methods, among our products are iouosalicylic acid, vhich on rapid heat-inr gives iodophenol, from which catechol can be obtained. ^^uinol, hydroq^uii'Oiie, paradihydroxy- benzene, 1-4 phendiol may be synthesized from salicylic acid. 25. First the salicylic acid is iodised or 'brominated so a.s to form 5 iodo- or 5 crom- salicylic acid which on fusion v/ith potash gives 2:5 dihydroxy "ceni'-oic acid. This "body on dry distillation yields quinol. This same tody may he prepared ty first nitrating the salicylic acid into the 5-nitro acid and then to the 5- amino salicylic acid, thence converting to the E-5 dihydroxy "benzoic acid hy the diazo method. llote: The 5-amino-salicylic acid is best pre- pared by the redaction of benzeneazoealicylic acid. 5-lTitrosalicylic acid on heating with lime gives p- nitrophenol, -..hich can be reduced to p- amidophenol . and treated as above. Salicylic acid yields gentisic acid by direct oxidation with potassium persulphate in alkaline solution. Anisic alde?iyde: p-methoxyben::oic alde- hyde CHO OCH E4. This liOdy is found in the volatile oil from the wood and the bark of the Chione glabra. It cari ce prepared from salicylic acid by first converting to the aldehyde then thru S-methoxy- benzoylacetic ester. Euxanthone xhis body exists in euarthic acid or Indian Yellov.-. It is found in the free state In coloring matter resulting from decomposition. Upon nitration, salicylic acid yields 5-nitro and upon reduction forms 5-arainosalicylic acid. The amino- acid gives gentisic acid by the diaso method. There are numerous other bodies that are prepared synthetically by means of the sali- cylic acid and its salts. 25, OUR Iffi'xHOD OP PREPAHATIOH. (4th Ruii) The materials used were pure sodium hydroxide and crystalline phenol. 120 grans of sodium hydroxide are dissolved in an equal weight of v.ater in a porcelain dish and cooled. This is slowly added to 260 grams of phenol in a shallow enameled pan, about 14xGxl". The mixture is well stirred up and kept cool. This gives a mixture v/hich is only slightly colored. It is now placed in the vacuum drying chest to ce evaporated to dryness. A vacuum of atout 2£" is maintained and the temperature is kept down to 50°-6C 2. The temperature must be just high enough so that the mass will barely boil. The temperature must ce kept low in ordei- to avoid charring. This is a very essential step in the process. The mass will gradually begin to thicken and in about three hours it will be completely solid. It is now removed from the drying chest and quickly powdered in an iron 26, mortar to a fine powder. The fine material is nov/ placed back in the drying chest, tut the steam is turned off, and it is dried for about half an hour. The pov/der thus obtained is sodium phenate. It is pinkish Y/hite in color, somev/hat hygroscopic and very soluble in vvater, acetone or alcohol. '.Vhen dry the sodium phenate is placed in the autoclave and the lid is put on. The autoclave used was made of copper, about 14" tall and about 6" in diameter and about S/16" thick. The lid was furnished with a lead gasket and it formed a tight joint with the body of the autoclave. The cover had a safety valve, a passage for gas and a well for a thermometer. The lid was fastened by means of a heavy bracliet. 27. Having placed the sodium phenate into the autoclave and the lid put in place, it is now tightly clamped in its seat. The gas inlet in autoclave cover is connected by means of heavy rubber tubing to an iron pipe containing calcium chloride. This pipe is about £' long and 1" in diameter; it is filled v;ith granular calcium c'nlor- ide protected at both ends with glass v.ool and wire gauze. The other end of this pipe is con- nected to a carbon dioxide tank cy means of extra heavy rubber tubing. The autoclave is now suspended in such a manner, that the bottom is immersed to a depth of atout 3" in running cold water. The carbon dioxide gas is turned on, the pressure in the auto- clave is not allowed to exceed 10 lbs. This is kept up for about an hour when the pressure is in- creased to 75 lbs. and at the same time the cool- ing is discontinued. V.lien no more carbon dioxide is being absorbed, the pressure is brought up to 75 lbs. again and allowed to stand for about one hour. £8. The cooling during the first stages of the carhon dioxide ahsorhtion is quite a desirable feature, because the temperature tends to rise considerably and if the mass is not cooled, phenol is split off, the mass chares and fuses together making further absorbtion diffi- cult. A paraffin bath is nov; brought under the autoclave so that the bottom vdll be immersed in paraffin to a depth of about 5". The temper- ature 01 the bath is gradually raised to 120° G and for four hours the temperature is carefully kept at 120°-140°C. The temperature of paraffin bath must ue taken and not the temperature in the well in the autoclave cover. The latter temperature is about 50° below the temperature of the paraffin bath. At the end of the four hours the auto- clave is allowed to cool off. V.'hen cool the auto- clave is opened, the mass is transferred to a dish and water added. The water is brought to a boil and a few o.c. of con. hydrochloric acid added. 29. This throws out the tarry matter and creosotic acids. This is separated in a separatory funnel. The solution is now cooled and more hydrochloric acid added. This throws out the impure sali- cylic acid. The impure acid is collected by fil- tration and is dried. Yield 44 gr. or 16;^ of the theoretical. With some modifications this is the Sohmitt method of preparation of salicylic acid. 30. EZPERILffiKTAI RUKS. (1st Run) lEO gr. of sodium hydroxide were ais- solved in an equal amount of water and mixed into 260 gm. of phenol. This was evaporated at 140°C and 14" vacuum. 350 grams of sodium phenate ob- tained. This was dark hrovai in color and very hygroscopic. The phenate was powdered up, placed in under a pressure of 10 Ihs., which was increas- ed to 50 Ihs. in the course of half an hour. The autoclave "became very warm during the passage of carbon dioxide. This pressure was kept up for two hours, then it was removed and the contents of the autoclave examined. The mass was dark "brown in color and of a thick pasty consistency; it smelt strongly of phenol. The cover ".vat re- placed and 50 lbs, of pressure applied from the oar'Lon dioxide tank. The autoclave was placed in a paraffin bath and heated for two hours at 130°-145°C. During this heating the pressure inside the autoclave went up to 60 lbs. At the end of the two hours the auto- 31, clave was allov;ed to cool off, and the contents were examined. The mass v.as of a dark brov.n color, moist and covered on top with fine cry- stals of phenol. This was transferred to an evaporating dish and dissolved in hot water. A little hydrochloric acid threw dov.Ti the tarry matter which was separated out. The remaining part was tested with ferric chloride after the excess of hydrochloric acid was neutralized with calcium cartonate. The test did not show the presence of salicylate. 32. EZPERIIJIEKTAI RUNS. (End Run) The same amounts of phenol and sodium hydroxide used as in the previous run. Evapor- ated at 100°C and 18" vacuum. The sodium phenate obtained was light brovm in color and hygroscopic. It was poudered , placed in the autoclave and carton dioxide gas passed in at a pressure of 10 lbs. and within half an hour this was gradually increaeed to 60 lbs. The autoclave became very warm. The press- ure was kept up for two hours, then removed and the contents examined. The mass was brown in color, moist and s;nelt of phenol. The cover was now replaced and 60 lbs. of pressure applied from the carbon dioxide tank. The autoclave was heat- ed for three hours at 150°-145°C. The pressure in the autoclave increased during heating to 70 lbs. At the end of the three hours the auto- clave was allowed to cool off and the mass examined, It was brown in color, somewhat moist and covered with crystals of phenol. This was treated as in the first run, and the ferric chloride gave a very strong test. However, there v.as not enough salicylate present to allow of its isolation in a oure state. 34. ESPSRIMEIITAL RUUS. (Srd Run) The same amounts of phenol tmd sodium hydroxide used. The mixture was evaporated at 60°C and 22" vacuum. The sodium phenate obtain- ed v.as pinkish v.hite in color and slightly hy- groscopic. It v.as powdered and placed in the auto- clave. Carbon dioxide gas was passed in at a pressure of 5 Ihs. and the autoclave v,as cooled by means of running cold water, as descriced in Run 4. In the course of an hour the pressure was gradually increased to 70 lbs. and kept up for another hour. The pressure was now removed and the mass in the autoclave examined. It v.'as light in color, dry, porous and it had a faint odor of phenol. After the cover was replaced, 70 lbs. of pressure was applied from the caruon dioxide tank ana the autoclave heated at 120-1400G for four hours. After the autoclave had cooled off the 35. mass was transferred to an evaporating dish. It was brownish gray in color, dry and had a faint odor of phenol. Hot v.-ater was added and after the tarry matter was separated out the impure salicylic acid was thrown out by another addit- ion of hydrochloric acid. [This was collected on the filter and dried. Yield 14 gr. or 4^. 36, PURIi'ICATIOlI Oi' THE lUPUHE ACID. The impure acid is dissolved in "boil- ing v.-ater and then neutralii:ed v/ith calcium oartonate and allowed to cool. Calcium sali- cylate separates oat in hard glistening crystals. A fairly pure acid yields almost pure white cry- stals, hut an impure acid gives brov.nish cry- stals. A second crystallization is ootained from the mother liquor. The calcium salt is again crystallized from water, until a pure white salt is ohtaiii- ed. It is now decomposed with hydrochloric acid and the pure sclicylic acid is washed with a little cold v.ater and finally crystallized out from dilute aloohol. This gives a very pure salicylic acid in the form of large prismatic crystals. After this purification only 29 gr. of pure acid was octained. or 6.3;: of the theo- retical yield. The chief impurities found in impure 37. acid are: phenol, creosotic acid due to impure phenol, para-hydroxy-benzoic acid and a-hydroxy- Iso-phthalic acid due to the presence of caustic BOda and to a too high or too low temperature in the manufacture. The presence of a small amount of Jm- puritiee causes the acid to crystallize from dilute alcohol in the form of a mass of inter- laced crystals instead of well defined large prisms. It is quite clear that with proper conditions present, the yield depends on the pressure. However, the highest pressure ob- tainahle with the equipment on hand v.as 75 lbs. per sq. in. , therefore no further runs were attem'oted. 38. TEE CH3LII£'i?Ry OF THE SCffi.IITT LETHOD. The chemistry of preparation of sali- cylic acid by the method proposed by Schinitt was explained by S. Tijmstra jun. (Ber.1905, 58, 1375-1365) Sodium phenate is prepared as in the Kolbe method C H OH * llaOH = C H OKa * H 6 5 6 5 2 When carbon dioxide is passed into the sodium phenate and heated to 120°-130°C under pressure the resulting product is ortho- BOdoxybenzoic acid (sodium phenoxide-ortho- carboxylic acid) OKa JQuH OUa.CgH^.COgH -- It is not identical with sodium sali- cylate. It has a greater dissociation tension than sodium salicylate. It slov?ly absorbs ammonia at ordinary temperatures. It is not S9. transformed into sodium salicylate when evapor- ated to dryness \\ith water. It changes complete- ly to sodium salicylate when dissolved in ace- tone. The ortho-sodoxyhenzoic acid, which is thus formed, on heating undergoes an isomeric change into sodium salicylate: OH COOlJa This shows that the C0„ enters direct- 2 ly into the nucleus. Y/hen sodium salicylate is heated in a closed tube for 2-12 hours at 248'^, it changes more or less completely into ortho-sodoxyhenzoic acid. 40. CQKGIUSIOU. The proper v^orking co adit ions for the process are outlined under "Our Method of Preparation." However, for larger yields pressure up to 125 lbs. per so. in, or even higher should ce used. To use an enameled autoclave with a stirring device would he of decided advan- tage, because it would yield a purer and more uniform product and it would materially cut down the time necessary for the completion of the reaction. The yield as well as the quality of the product depends mainly on three requisites; the sodium phenate must not ce charred, it must be dry and well powdered; the carbon diox- ide must bo dry; the temperature must be closely controlled. 41. RE?ESE^TCES . Neues HandwOrterlDuoh der Cheraie - 1890. Dictionnaire de Ghiinie - 1906. Thorp, Dictionary of Applied Chemistry, 7.4, - 1913. Die SyuthetiBchen Darstellimgsmethoden der Zohlenstoff-Verbindungen, Dr. Zarl Elbs - 1689. r/atts, Dictionary of Chemistry, V.5, - 1692. J. Chern Soc. 114. 11, 137-8. Ber. S. [Dijmstra, jun. , 1905, 36, 1375-65.